U.S. patent application number 11/914055 was filed with the patent office on 2009-08-20 for assembly for adjusting an optical element.
This patent application is currently assigned to CARL ZEISS SMT AG. Invention is credited to Ernesto Lopez-Real, Thomas Schletterer, Armin Schoeppach, Manfred Steinbach.
Application Number | 20090207511 11/914055 |
Document ID | / |
Family ID | 36649826 |
Filed Date | 2009-08-20 |
United States Patent
Application |
20090207511 |
Kind Code |
A1 |
Schoeppach; Armin ; et
al. |
August 20, 2009 |
ASSEMBLY FOR ADJUSTING AN OPTICAL ELEMENT
Abstract
An assembly for fixation or adjusting of an optical element (1)
with, regard to an outer mount or support (4) wherein the optical
element (1) is alignable with regard to a structure of the optical
arrangement, particularly the objective structure or the objective
barrel, having an optical axis or with regard to neighbouring
mounts by means of an adjusting arrangement, is characterized in
that the adjusting arrangement comprises at least an elastic means
(9), particularly a spring, an elastic rod or stick, an elastic
tape or an elastic gear wheel or an elastic gear box by which a
force or a torque is applicable to the optical element (1). The
assembly is particularly suitable for use in a microlithographic
exposure apparatus. In some embodiments an intermediate ring (27)
positioned between the optical element (24) and the outer mount or
support (26) is used to reduce deformations.
Inventors: |
Schoeppach; Armin; (Aalen,
DE) ; Steinbach; Manfred; (Jena, DE) ;
Schletterer; Thomas; (Stadtroda, DE) ; Lopez-Real;
Ernesto; (Jena, DE) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
CARL ZEISS SMT AG
Oberkochen
DE
|
Family ID: |
36649826 |
Appl. No.: |
11/914055 |
Filed: |
May 9, 2006 |
PCT Filed: |
May 9, 2006 |
PCT NO: |
PCT/EP2006/004337 |
371 Date: |
August 8, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60679687 |
May 9, 2005 |
|
|
|
Current U.S.
Class: |
359/822 ;
359/811 |
Current CPC
Class: |
G03F 7/70825 20130101;
G03F 7/70258 20130101; G02B 7/023 20130101; G02B 7/005
20130101 |
Class at
Publication: |
359/822 ;
359/811 |
International
Class: |
G02B 7/02 20060101
G02B007/02 |
Claims
1. An assembly for positioning of an optical element with respect
to a mount, wherein said optical element is positionable by a
positioning arrangement, wherein said positioning arrangement
comprises at least a single elastic means that one of shifts and
moves said optical element in two degrees of freedom independently
by exerting one of a force and a torque on one of the optical
element itself, a flange of said optical element, a holder
enclosing said optical element and a support enclosing said optical
element.
2. The assembly of claim 1, wherein one of said holder and said
support comprises at least a single isostatic mount to which one of
a force and a torque is applied by said elastic means wherein said
isostatic mount is adjustable in at least two degrees of
freedom.
3. The assembly of claim 2, wherein said at least one isostatic
mount is one of a bipod and a bipod structure.
4. The assembly of any of claim 1, wherein said elastic means
comprises one of a reduction means, a spring, an elastic lever an
elastic rod, an elastic tape, an elastic belt, an elastic
gear-wheel and an elastic wheel.
5. The assembly of claim 1, wherein said elastic means is one of
moveable and shiftable in each of said two degrees of freedom one
of by two separate means, by two piezoelectric actuators, by two
electostrictive actuators, by two motors, by two pneumatic means
and by two hydraulic means.
6. The assembly of claim 1, wherein three elastic means are
provided that each are one of shiftable and moveable in two degrees
of freedom.
7-13. (canceled)
14. An assembly for one fixation an adjusting of an optical element
with regard to one of an outer mount and a support, wherein said
optical element is alignable with regard to one of a structure of
an optical arrangement, an objective structure, an objective barrel
having an optical axis and neighbouring mounts by means of an
adjusting arrangement, said adjusting arrangement comprises at
least one of an elastic means a spring, an elastic rod, an elastic
stick, an elastic tape, an elastic gear wheel and an elastic gear
box by which one of a force and a torque is applicable to said
optical element. said optical element is positioned in an inner
mount and one of said force and said torque for adjusting of said
optical element is applied to said inner mount.
15. (canceled)
16. The assembly according to claim 14 wherein said inner mount is
connected to said outer mount by means of at least one intermediate
part.
17. The assembly according to claim 16, wherein said at least one
intermediate part comprises a first bearing element connected to
said inner mount, an intermediate element and at least one
adjusting means by which one of a force and a torque is applicable
for one of adjusting and positioning of said optical element by
means of an elastic attacking means.
18. The assembly according to claim 17, wherein said elastic
attacking means comprises one of an elastic rod serving as a lever
arm of a force in a lever, an elastic tape for transmission of a
torque by means of at least one roll, an elastic gear wheel in a
reduction gear for transmission of a torque, any elastic means
transmitting a force onto said intermediate element, a spring
transmitting a force onto said element, a spiral spring
transmitting a force onto said intermediate element, and an elastic
tape for transmitting a force onto said intermediate element.
19. The assembly of claim 18, wherein said intermediate element is
rigid or stiff and at least less elastic than said attacking
means.
20. The assembly of claim 14, wherein at least a second bearing
element is provided, said second bearing element being connected to
said outer mount.
21. The assembly of claim 17, wherein said at least one adjusting
means comprises at least one elastic lever attached to said
intermediate element by one of its distal ends.
22. (canceled)
23. (canceled)
24. The assembly of claim 21, wherein said at least one lever is
connected at its second distal end with at least one of a fixation
element, an element comprising at least one holes defining a
predetermined position, an actuator and an adjustor.
25. The assembly according to claim 24, wherein said actuator
comprises one of an electromagnetic actuating means, an
electrostrictive actuating means, a magnetostrictive actuating
means, a pneumatic actuating means, a hydraulic actuating means and
a mechanic actuating means.
26-36. (canceled)
37. An assembly for one of fixation, adjusting and or positioning
of an optical element with regard to an outer mount, wherein said
optical element is one of alignable and positionable with regard to
one of a structure of an optical assembly, a barrel of an objective
having an optical axis neighbouring mounts and neighboring supports
the positioning or adjusting means is embodied by an intermediate
ring positioned between said optical element and said outer
mount.
38. The assembly according to claim 37, wherein said optical
element is received in an inner mount and said intermediate ring is
borne between said inner mount and said outer mount.
39. The assembly according to claim 37, wherein adjusting means or
actuators are arranged at said intermediate ring.
40. The assembly according to claim 37, wherein at least one of a
bearing elements of said assembly, a ring segment of said assembly
and said intermediate ring is generated by eroding.
41. The assembly according to claim 40, wherein one of said
positioning means and said adjusting means comprises at least a
single elastic element that is installed under tension in one of
said intermediate ring and said ring segment and one of said
positioning means and said adjusting means applies one of two
forces and torques being in equilibrium.
42. The assembly according to claim 41 wherein one of said
positioning means and said adjusting means comprises at least an
elastic element that applies one of a force and a torque to said
intermediate ring by application of a torsion to said elastic
element.
43. The assembly according to claim 42, wherein one of said torque
and said force is applied to said intermediate ring by means of one
of at least one reduction element, and a projection in the form of
a block.
44. An assembly for one of fixation and adjusting of an optical
element with regard to one of an outer support and a mount, wherein
said optical element is alignable with regard to one of a structure
of an optical assembly, a structure of an objective, having an
optical axis and a neighbouring mount by means of at least one
adjusting arrangement the at least one adjusting arrangement
comprises an elastic element to which one of a force and a torque
is applied.
45. The assembly according to claim 44, wherein said optical
element is positioned in one of an inner mount and an inner
ring.
46. (canceled)
47. An adjusting assembly comprising an arrangement for one of
moving and shifting one of an optical element and a support one of
enclosing and supporting an optical element, wherein said
arrangement comprises one of at least a single mechanic
transmission and a single mechanic reduction arrangement having a
work arm supporting an optical element of a microlithographic
exposure apparatus and a lever arm at least one of said arms is at
least one of made of an elastic material and is linked to an
elastic means for transmitting a force.
48. (canceled)
Description
[0001] The present invention pertains to an assembly for fixating
or adjusting of an optical element with regard to an outer support
wherein the optical element is alienable with regard to a structure
of an optical assembly having an optical axis, particularly to a
structure of an objective, or with regard to neighbouring supports
by means of an adjusting arrangement.
[0002] Optical elements have to be defined in very stable positions
in holders or supports and may not experience any change of
position or deformation after these components have been combined
with other structural elements. This is particularly required in
high performance optics as used in micro lithography. Nethertheless
mounting and process steps requiring a change of position cannot be
avoided. Regularly, these changes are corrected by tunable
intermediate steps; these steps, however, implicate an iterative
sequence of mounting, demounting, correcting and renewed mounting
steps and often permit only limited correction restricted by the
degrees of freedom. A robust and simple adjusting mechanism
comprising the barrel and the support of the element would be
desirable. A last correcting step regarding all six degrees of
freedom should be realized without a step of demounting; in the
same time all requirements of an optical assembly comprising at
least a single optical element should be met as are stiffness and
decoupling of deformation.
[0003] From US 6 229 657 B1 an assembly of an optical element and a
mount is known, in which the optical element is coupled by means of
numerous lugs to a rigid intermediate ring, which itself is coupled
by adjusting members or passive decouplers to the mount for
connection to a housing and/or a further mount. Actuators are
provided that
[0004] From US 2002/0163741 an optical element holding apparatus is
known that comprises holders and actuators positioned tangentially
with regard to a lens. An assembly for positioning an optical
element in an optical assembly, particularly in a projection
objective for semiconductor lithography, is described in EP 1 245
982 A2 which is connected to an outer support by three bearings
positioned at the circumference of the optical element. Connecting
members in form of leaf springs are provided that bring movements
generated by manipulators positioned in the support to the optical
element.
[0005] From US 2005/0002011 A1 a support mechanism and an exposure
apparatus comprising the support mechanism are known. The support
mechanism for supporting an optical element includes a first
support member for supporting the optical element and a second
supporting element coupled to the first support member via an
elastic member, and a forcing member for applying a force to the
elastic member. When the forcing member applies a force to the
elastic member, a position and/or an orientation of the optical
element are adjustable, or the relative positions between the first
and the second support members are changed. The elastic member
deforms in a radial direction of the optical element or about a
rotational axis perpendicular to both a radial direction of the
optical element and a direction into or parallel to the optical
axis of the optical element.
[0006] The technology shown in FIG. 3 of this document permits
pressing on a small bridge connecting two flat springs 222 and 224
by means of a bulbar part 232 of a compression member or micrometer
screw 230 and thereby to elastically deform a lens L held by a
support member 210. An adjusting of the lens L in two degrees of
freedom is realized at the same time. By coupling of these two
degrees of freedom compulsory forces are realized that partially
have to be taken by both a lens barrel and the support member
210.
[0007] From US 2003/0234918 A1 adjustable soft mounts in a
kinematic lens mounting system are known. A mounting system for
mounting an optical element such as a deformable lens for use in a
lithographic exposure apparatus employs a plurality of adjustable
soft mounts to support it and apply vector and moment forces at its
peripheral portions so as to correct its shape. These adjustable
soft mounts each have an elastic member such as a coil spring, a
cantilever plate spring or a torsion spring and a force-adjusting
member such as an adjusting screw or bolt that varies the force
applied by the elastic member to a peripheral portion of the
optical element. The soft mounts are less rigid than position
defining mounts that support the optical element at a desired
portion.
[0008] From this document, it is principally known to provide
tangentially rigid mounting structures having a constraint in one
direction, i. e. the tangential direction, and allowing five
degrees of freedom associated with two direction of forces (vector
forces) and three direction of torques (momentum forces) (example
shown in FIG. 6). In another embodiment (FIG. 7) according to this
document, a soft mount is realized by a low-stiffness spring having
one end fixed to a peripheral point of an optical element or its
flange, so as to apply an upward force thereonto.
[0009] According to FIG. 11 of this document, a rigid mounting
structure is constrained in the tangential and axial directions. An
actuator comprised of a static adjustor, a soft spring and a voice
coil motor is provided to the clamping structure. Static moment
forces can be applied to the structure through off-axis mechanisms
such as leaf springs and adjustors wherein dynamic adjustments may
be added to these mechanisms.
[0010] It is an object of the present invention to improve an
optical assembly that positioning of the optical element is
achieved in a simple manner.
[0011] According to the invention this object is attained by an
assembly characterized in that the positioning arrangement
comprises at least a single elastic or resilient means that shifts
or moves the optical element in two degrees of freedom or two
directions independently by exerting a force or a torque on a
flange of the optical element or a holder or a support enclosing
the optical element.
[0012] According to the present invention "positioning" comprises
adjusting of an optical element in a controlled way like with an
open or closed loop control and comprises also a single adjustment
for the single calibration of the system.
[0013] According to the present invention the member exerting a
force and/or a torque on the flange of the optical element or on a
support holding the optical element may be entirely elastic or may
be comprised of a resilient material that partially is elastic and
partially is plastic. According to the invention the use of a
resilient member may be appropriate when the optical element needs
to be positioned in a unique positioning operation.
[0014] According to the invention the principle is used that the
work generated by a force applied to a work arm of a lever formed
by an elastic body, for instance a stick of leaf steel, is only
partially transformed to a work exerted along the direction of the
load arm, but is, for the other part, needed for distorting of the
work arm, and, if the load arm likewise consists of an elastic
material, is also needed to distort the load arm. Therefore a
considerable share of the work exerted by the force has to be used
for distortion if it is intended to reposition the load arm.
Therefore, according to the invention at least one of the work arm
or the load arm consists at least partially of an elastic
material.
[0015] For adjusting or for a single positioning of an optical
element, particularly a lens, a mirror, a reticle or an aperture,
or the like, this effect is used to enlarge the reduction of an
external influence to adjust or position an optical element. If,
for instance, a rigid work arm of the state of the art having a
lever distance of 5 mm leads to a movement of the load arm of 5
.mu.m, this implies a reduction of 1:1000, and therefore a work arm
having a length of thousand times the length of the load arm; such
a reduction is realized by a work arm by far smaller according to
the invention as a part of the work is always spent to distort the
work arm and/or the load arm.
[0016] In reversed application of this principle, the same
application of a force applied to a work arm produces, according to
the elasticity of the work arm and/or the load arm a
correspondingly weaker and therefore more precise movement of the
load arm. For estimating precisely the movement of the load arm it
is prerequisite to know exactly the elasticity value that--at least
over a wide range--is many times a constant or has a known
characteristic line as a function of the distance.
[0017] The teaching of the present invention explained above with
respect to the use of a lever as an adjusting means is applicable
to all means for transferring a force or a torque directly on a
flange of an optical element or on an inner support or inner ring
supporting the optical element. Thereby gear boxes with gear wheels
equipped at least partially with an elastic material, rolls
together with elastic tapes, springs in form of helical or spiral
springs, or any other means appropriate to receive deformation
energy.
[0018] According to the teaching of the present invention two
forces or two torques or a combination of one force and one torque
act on a single element or point of a hinge.
[0019] Advantageous embodiments of the invention are represented by
the depending claims, the description and the drawings.
[0020] According to the present invention an assembly for
positioning of an optical element with respect to a mount wherein
the optical element is positionable by a positioning arrangement is
provided. The assembly is characterized in that the positioning
arrangement comprises at least a single elastic or resilient means
that shifts or moves the optical element in two degrees of freedom
or two directions independently by exerting a force or a torque on
the optical element itself, on a flange of the optical element or a
holder or a support enclosing the optical element.
[0021] According to this invention "to shift" means a linear motion
whereas "to move" comprises a linear or a rotational motion.
[0022] Further, the assembly may be characterized in that the
holder or the support comprises at least a single isostatic mount
to which a force or a torque is applied by the elastic means
wherein the isostatic mount is adjustable in at least two degrees
of freedom.
[0023] Preferably, the at least one isostatic mount is a bipod or a
bipod structure.
[0024] Preferably, the elastic or resilient means comprises
reduction means, particularly a spring, an elastic lever or rod, an
elastic tape or belt, an elastic gear-wheel or an elastic
wheel.
[0025] In an advantageous embodiment the elastic means is moveable
or shiftable in each of the two directions or degrees of freedom by
two separate means, particularly by two piezoelectric or
electostrictive actuators or by two motors or by two pneumatic or
hydraulic means.
[0026] Further it is advantageous if three elastic means are
provided that each are shiftable or moveable in two directions or
two degrees of freedom.
[0027] Preferably the assembly is characterized in that the three
elastic means are positioned at angles of substantially 120.degree.
apart from each other and wherein the acuators are positioned at
angles of between 60.degree. and 120.degree. between them,
preferably at 90.degree. between them.
[0028] Further, the assembly may be characterized in that the
elastic means or each of the elastic means is movable or adjustable
by means of at least one screw, particularly by means of a
micrometer screw.
[0029] In a further embodiment the at least one screw is borne in
an outer ring or in an interstitial or intermediate ring.
[0030] In another embodiment the interstitial ring is coupled in
that way to the outer ring that the interstitial ring is statically
defined.
[0031] Preferably, the assembly is characterized in that the
interstitial ring is coupled to the outer ring by means of spring
elements.
[0032] In a further embodiment the spring elements are distributed
over at least substantially equal distances from each other between
the interstitial ring and the outer ring.
[0033] In another advantageous embodiment the spring elements are
stiff.
[0034] It is advantageous if the optical element is supported by an
inner holder and if the force or the torque to adjust the optical
element is applied to the inner holder.
[0035] Preferably, the inner holder is connected to an outer mount
by an intermediate part or ring wherein at least a single adjusting
means is applied to the intermediate ring. As a rule, three
adjusting assemblies positioned at a distance of 120.degree. are
applied to the inner ring to ensure a possibility of adjusting in
all six degrees of freedom. If, however, an adjustment is needed in
less than six degrees of freedom, less than three adjusting
assemblies may be provided.
[0036] In an advantageous embodiment the at least one intermediate
part is constructed in that way that it comprises a first bearing
member connected to the inner support, an intermediate element and
at least a positioning or adjusting means by which a force or a
torque to adjust or readjust the optical element by an elastic
means, applied to the intermediate element is applicable to the
optical element from the intermediate element.
[0037] Hereby, advantageously, an elastic rod or stick serving as a
work arm of a lever, an elastic tape or belt for transmitting a
torque by means of at least one roll, an elastic gear wheel in a
reduction gear box for transmitting of a torque or another elastic
means, particularly a spring, preferably a spiral spring, or an
elastic tape or belt for transmitting a force or a torque on an
intermediate element is provided and therefore serves as an elastic
means to which a force or a torque is applied.
[0038] Preferably, an intermediate element consists of a rigid or
at least a less elastic material than that forming the means that
applies the force or the torque.
[0039] Together with the adjusting means at least a second bearing
member is used that is connected to the outer holder or
support.
[0040] Advantageously, each adjusting means comprises at least an
elastic lever fixed by one of its distal ends at the intermediate
element to exert a force or a moment on the intermediate element or
to rotate it.
[0041] For instance, a single lever is provided that, with regard
to the optical element, is aligned in any direction. However, there
may be several levers, that may be lifted and lowered in the
direction of the optical axix of the optical element. Also a
rotational movement of the levers is possible whereby the levers
may undergo a torsion at the same time. The rotational movement of
the levers may take place in the area of the optical element.
[0042] The lever may be adjusted in a preferable way, for instance,
be rotated and/or be adjusted in axial and/or radial direction.
[0043] For a unique positioning and fixation of the assembly it is
sufficient if the at least one lever is fixated with its second
distal end at a fixation element, especially by means of a
positioning element have a hole at a predetermined position
(Lochmaske). It is to understood that by exchange of such elements
having a hole or a plurality of holes that are, for instance, fixed
at the outer support, other positions of the inner support and
therefore of the optical element may be adjusted. In the
alternative, an actuator may be provided to change the position of
the embodiment.
[0044] Advantageously, the actuator comprises an electromagnetic,
an electrostrictive, a pneumatic, a hydraulic or a mechanical means
for actuating the actuator.
[0045] In an advantageous embodiment of the assembly the first
bearing members are positioned at least partially in recesses or
grooves of the inner support.
[0046] In a corresponding way the second bearing members may be
positioned in recesses or grooves of the outer support.
[0047] Preferably, the second bearing members are each embodied as
cardanic hinges to permit tilting of the intermediate member in all
directions of space.
[0048] In an advantageous embodiment of a cardanic hinge, the
second bearing members each comprise leaf spring hinges or a pair
of metal plates
[0049] Advantageously, it may be provided that two of the thin
metal plates extend in a tangential or axial direction under an
acute or an obtuse angle with regard to the intermediate element in
an
[0050] In the same way it is advantageous if the first and/or the
second bearing elements are embodied as solid body hinges,
preferably as leaf springs.
[0051] Additionally, it is provided advantageously, that bearing
elements or hinge elements, preferably leaf springs, comprise an
intermediate member in form of a cross to decouple radial torques
or moments.
[0052] The intermediate parts may be produced in different ways,
for instance, in that the intermediate parts are produced from at
least one basic element by cutting out the hinges in the at least
one basic element.
[0053] In the same way the intermediate parts may be generated by
eroding of a original body.
[0054] In a special embodiment of the invention it is provided that
intermediate parts are embodied as ring segments or as a closed
ring. In the same way, it is imaginable that the intermediate parts
or elements are embodied at least partially as rings or ring
segments or that they are connected by such.
[0055] In an advantageous embodiment of the invention the
intermediate ring or the ring segments are fixed by at least a
first bearing element at the inner ring and at least by a second
bearing member at the outer ring.
[0056] The invention also pertains to an embodiment for fixation
and adjustment of an optical element with regard to an outer
support, wherein the optical element is alignable with regard to a
structure of an optical assembly, especially to an objective
structure, having an optical axis or with regard to neighbouring
mounts, adjustable by means of an adjusting means.
[0057] Such an embodiment is characterized in that the adjusting
means is embodied by an intermediate ring positioned between the
optical element and an outer support or holder.
[0058] Also in this embodiment of the invention it is advantageous
if the optical element is borne by an inner mount and if the
intermediate ring is borne between the inner mount and the outer
mount.
[0059] Preferably, adjusting elements are positioned at the
intermediate ring that may be generated by eroding the intermediate
ring.
[0060] An embodiment of the invention proves as advantageous
according to which the adjusting device comprises at least a single
optical element that is installed tensed up in the intermediate
ring or in the ring segment and that applies two forces and/or
torques being in equilibrium with regard to each other.
[0061] Advantageously, the adjusting device comprises at least an
elastic element to apply a tensing up force or a torque against the
outer ring or the intermediate ring.
[0062] The torque or the force is exerted preferably by at least a
single reduction means on the intermediate ring, preferably by a
projection having the form of a block.
[0063] The invention is related also to an assembly for fixation or
adjustment of an optical element with regard to an outer mount or
support wherein the optical element is alignable with regard to a
structure of an optical arrangement, especially an objective
structure, having an optical axis or with regard to neighbouring
mounts by means of at least an adjusting arrangement.
[0064] Hereby, the assembly is characterized in that the at least
one adjusting arrangement comprises at least one elastic element to
which a force or a torque is applied.
[0065] In an advantageous embodiment of the assembly the optical
element is supported by an inner support.
[0066] Further, the invention is also related to a projection
exposure apparatus for micro lithography. The projection exposure
apparatus is characterized in that the projection objective is
equipped with at least one assembly for adjusting or positioning of
an optical element as described above.
[0067] The invention will hereinafter be explained in more detail
through examples of embodiments with references to the drawings,
wherein:
[0068] FIG. 1a is a perspectivic top view on an optical element
supported by an inner support wherein the optical element is borne
in an intermediate part having two adjusting means,
[0069] FIG. 1b shows a detail of FIG. 1a,
[0070] FIG. 1c is a schematic view on elements of FIG. 1a,
[0071] FIG. 2a-c are perspective views of a bearing element
arranged between an outer support and the intermediate part,
enlarged,
[0072] FIG. 3 is a section of an inner support and an outer support
having an intermediate part arranged between them according to
FIGS. 2a, b,
[0073] FIG. 4 is a top view of an optical element arranged between
an inner support and an outer support comprising three intermediate
parts
[0074] FIG. 5 is a view of an intermediate part,
[0075] FIG. 6a is a view of an alternative of an elastic means for
adjusting of an optical element positioned in an inner ring,
[0076] FIGS. 6b, c are detail views of FIG. 6a, enlarged,
[0077] FIG. 7a-c are further detail views of intermediate
parts,
[0078] FIGS. 8a, b shows the concept of the invention of a
reduction controlled by rigidity compared with the lever principle
according to the state of the art,
[0079] FIGS. 9a, b a schematic sectional view on an adjusting
mechanism comprising two micrometer screws or two levers for
adjusting an optical element, and
[0080] FIGS. 10, 11 other embodiments comprising adjusting
mechanisms.
[0081] An optical element 1 (FIG. 1a), for instance a lens or a
mirror, through the center A of which an optical axis a extends in
the axial direction is supported in an inner ring or inner mount 2.
The position of the optical element 1 with regard to the inner
mount 2 and an outer mount 4 may be adjusted by an adjustor
comprising an intermediate part 3 for a single time or may be
changed repeatedly. The assembly preferably comprises three
intermediate parts 3 that are arranged symmetrically between the
outer circumference of the inner mount 2 and the inner
circumference of the outer mount 4.
[0082] Each intermediate part 3 comprises a first bearing element 5
connected to the inner mount 2, a second bearing element 6
connected to the outer mount 4, and an intermediate part 7
positioned between the bearing elements 5, 6, for instance being
embodied as a solid block. The bearing elements 5, 6 each consist
of a thin elastic material and constitute, together with the
intermediate part 7, a statically defined bearing of element 1.
Bearing element 5 has lateral grooves that constitute a small
bridging element or catwalk 8 connecting element 5 to the
intermediate element 7 and ensure a sufficient flexibility or
suppleness of bearing element 5 in the direction of its radial or
tangential axis.
[0083] Bearing element 6 (FIG. 1b) is an elastic element that is
rotable in two degrees of freedom. It may be replaced by a hinge
arrangement as shown in FIG. 2. The elastic element 6 is shown
again in FIG. 1b wherein rod 9 having two defined rotational axes A
and B exerts a rotation of element 6 in the direction of axes A'
and B' of element 6. Two rotational degrees of freedom are exerted
independently of one another. Each rotational degree of freedom may
be converted to a translational degree of freedom by means of
levers or arrangement of levers connected with each other by
hinges.
[0084] Therefore two rotational or two translational degrees of
freedom or a combination of a rotational and a translational degree
of freedom are realized independently by the present invention.
[0085] Bridging element 8 comprises a point of attack wherein two
forces or two torques or a combination of a force and a torque act
on the support 2 or directly on the optical element 1 if there is
no support. According to FIG. 1, bridging element 8 is a link
between the support 2 or the optical element 1 and the adjusting
means. Preferably, the optical element 1 is held isostatically by
three bearing points, eventually by means of an inner ring or an
inner support. This means, that by each adjusting arrangement two
degrees of freedom are adjusted independently.
[0086] At intermediate element 7 an elastic stick 9 extending in
radial direction with respect to the optical element 1 is fastened
that serves as adjustor. When a torque applied to stick 9 is
exerted on intermediate part 7 in direction of arrow B the
intermediate part 7 is moved and causes a bending of bearing
element 6.
[0087] The stick 9 has a length C that is a multiple of a length d
between the point of attack of stick 9 within block 7, i. e. at its
center, and the contact line of catwalk 8 at block 7. The relation
C:d constitutes a regular reduction relation between the length of
the work arm and the length of the load arm. As, however, stick 9
is made of a highly elastic material, for instance a spring steel,
the relation of reduction is increased by far, for instance by a
factor 100. By a fixed expense of force a much smaller and
therefore much more sensible adjustment is in axial and tangential
direction is realized than would be possible according to the state
of art using a rigid or at least substantially rigid positioning
means.
[0088] In a schematic view (FIG. 1c) it is shown how elements 5 and
6 are moved when element 7 is bent by means of stick 9 in direction
51. It is to be remarked that both elements 5 and 6 contain hinge
points a, b and c. Thereby it is possible to exert a considerable
change of the position of optical element 1 in the direction of the
optical axis (z-axis) without exerting any considerable movement in
radial direction.
[0089] In another embodiment (FIGS. 2a, b) an intermediate part 10
appropriate for insertion between an inner mount and an outer mount
comprises a block 11 that constitutes an intermediate part wherein
an attacking means for transmission of a torque or of a force onto
block 11 attacks the block 11, and in that way the inner mount.
Block 11 is connected directly to an inner mount or to a thin metal
plate 13 that belongs to the inner mount by means of a short
torsion stick or an element 12 in form of a cross. This arrangement
constitutes a first bearing element; the inner ring positioned at
three bearing points has a bearing statically substantially or
approximately defined.
[0090] On its other side, block 11 is linked to another element 16,
that has the form of a block, by means of two metal plates 14, 15
arranged under an obtuse angle with regard to each other. Element
16, for its part, is connected to an outer mount by means of two
metal plates 17, 18 inclined with regard to each other. Metal
plates 14, 15, together with element 16 and metal plates 17, 18,
constitute the second bearing element that constitutes a cardanic
hinge or joint and that permits tilting of the inner mount in all
directions of space at three bearing positions. At block, 11 a
torque may attack in the same way by an elastic stick as shown by
FIG. 1.
[0091] The intermediate part or adjusting means 10 shown in FIGS.
2a, b is, for instance, inserted in a recess of outer mount 19
(FIG. 2c) in order to tilt block 11 by means of a stick 20 as
described hereinafter. Elements 12 (FIG. 2a) and 21 (FIG. 3) are
another embodiment of a statically defined bearing comprising the
elements 5 and 8 as shown by the embodiment of FIG. 1.
[0092] Elastic element 6 of FIG. 1a may be replaced by a "cardanic"
arrangement of hinges as shown in FIG. 2c. Two cardanic axes 100
and 200 are provided wherein axis 200 may be--but not
necessarily--rectangular with respect to axis 100. A rigid or an
elastic or flexible lever 300 may be fixed at the element 12
whereby a recess or an excavation in element 16 is necessary to
permit a free movement of lever 300. When lever 300 is activated in
the direction of the optical axis, 51 part 11 and part 16 exert a
tilting movement about axis 100. When lever 300 is activated in
direction of axis 50 part 16 remains in its rotational position
whereas part 11 rotates about its axis 200. Thereby ring 2 and
optical element 1 is positionable by two axes 100 and 200 of
rotation, i. e. an axial and a tangential rotation. The position of
axis 100 is defined by the arrangement of holding elements 17 and
18.
[0093] Generally, an elastic element 6 rotatable in two degrees of
freedom as shown in FIG. 1 may be replaced by a hinge arrangement
comprising two defined rotational axes as shown by FIG. 2a -c.
[0094] Adjusting means 10 (FIG. 4) are distributed in triplicate
over the circumference of the outer support 19 to permit a
positioning, moving or shifting of the lens 23 or another optical
element as a mirror or a reticle borne in the inner support 22.
Therefore, bearing an optical element in the centre of a concentric
support system according to the invention permits to adjust an
optical element in all 6 degrees of freedom wherein each degree of
freedom is adjustable independently of the others. Coupling of two
or more degrees of freedom as disadvantageously taught by the state
of the art is avoided, at least substantially.
[0095] Further embodiments (FIGS. 6a, b, 7) show an extended
principle of the invention wherein the intermediate part 7 of FIG.
1 or intermediate part 11 of FIGS. 2a -c, respectively, are
embodied by a ring having a plurality of segments or having a
closed form.
[0096] The last form is shown by FIGS. 5, 6a where an optical
element 24 is borne in an inner mount 25. Thereby, an intermediate
ring 27 is positioned between inner mount 25 and outer mount 26. An
advantage of such a system consists in that three components, an
inner ring or inner support 25, an interstitial or intermediate
ring or support 27 and an outer ring or barrel 26 bear an optical
element 24 and thus compulsory forces, e. g. acting on the outer
support 26, are reduced; and therefore the deformations.
[0097] Appropriate adjusting arrangements are shown by FIGS. 7a, b,
c. These adjusting arrangements comprise a single or plural elastic
means that are embodied by thin spring sticks or torsion springs
that may be bent, for instance, in form of a U, or that are
embodied by a thin wire.
[0098] In the embodiment shown in FIG. 6a an optical element 28 is
borne in an inner mount or in an inner ring 29 that, on its part,
is arranged in an intermediate ring 31. This ring 31 is borne in an
outer support or an outer ring 33 by means of second bearing
elements 32. The outer support 33 is borne in the barrel of the
objective by means of flexures or elastic elements 34 that may be
embodied by wires. To retain the positioning of the optical
element, additionally, fixating sticks 35, 36 are embodied between
the outer support and the elastic elements 34.
[0099] The bearing elements 30, 32 shown in FIG. 6a are embodied in
that way and permit high mobility of the inner mount 29 and
therefore of element 28 with regard to the barrel or the support of
the objective when the inner ring 29 is distorted so as to realize
a statically defined bearing of each of the intermediate ring 31
and the inner ring 29,
[0100] Instead of intermediate ring 31 as shown by FIG. 6a, in the
alternative, intermediate elements 37 (FIG. 6b) that, for instance,
have a rectangular form in the top view may be employed together
with bearing elements 38, 39. The bearing elements 38, 39 are
symmetrical with regard to the radial axis of the optical element
28, the intermediate elements 37 and the barrel of the objective.
Thereby, bearing element 39 is realized in that way that it
embodies a statically defined bearing of inner ring 29. The bearing
element 38 may be considered as a stiff spherical joint that may be
distorted about all axes with respect to a rotation.
[0101] The optical element 28 may be tilted even in an easier way
when bearing elements 40, 41 (FIG. 6c) are positioned in the region
of the outer edges directed to the inner mount 31 or the outer
mount, each shifted with respect to the radial axis of intermediate
elements 42 in the region of the outer edges that are facing the
inner mount 31 and the outer mount, respectively. The intermediate
elements 42, preferably, have a form wherein the edge faces the
inner mount 31 and the edge faces the outer mount 33 have a
curvature that, preferably, corresponds to that of the inner mount
31 and to that of the outer mount. The bearing elements 40, 41 are
assembled in a way analogous to that of the bearing elements 38,
39.
[0102] According to another embodiment (FIGS. 7a, b) intermediate
parts 43 are provided between the inner mount 31 and the outer
mount 33 that are assembled substantially as the intermediate parts
42 (FIG. 6c). Apart from bearing elements 40, 41 positioned in a
shifted arrangement and as provided according to FIG. 6c elastic
sticks 44 are provided. Thereby, movements of the inner mount 31
with regard to outer mount 33 are generated by distortion of the
intermediate elements 43, 46. The distortions are realized by
distortion of elastic sticks 45 according to the embodiment shown
in FIG. 7a.
[0103] In an alternative embodiment (FIG. 7b) an intermediate
element 46 is distorted by a bracket or a clamp 47 that is bent
according to FIG. 7c. In both of the embodiments shown in the end,
no resulting forces or moments are exerted on the distorted
intermediate element 43 or 46, respectively.
[0104] FIG. 8a shows the classic lever principle in the example of
a two-arm-lever 48 that is borne at a rotation point 49. Thereby a
purely geometric correlation is given. Thus the work arm V2 as a
function of the lever arm of the force:
V2=d.times.V1.
When elastic materials are applied for such a lever having two arms
or only a single arm wherein the spring rigidity of the lever arm
of the force is c1 (FIG. 8b) and wherein the spring rigidity of the
work arm is c2 the reduction or transmission changes from
V2=d.times.V1 to V2=c1/(c1+c2).times.V1. Herein a transmission or a
reciproque transmission (reduction) depends on the stiffness of the
constructive elements; this can, by instance, mean:
c2=100.times.c1.
[0105] This principle is known and is, for instance, realized by a
Michelson spring. When considering the energy balance of the
assembly shown in FIG. 8b the work stored in the elastic elements
is reciprocal to the stiffness of the elements. This means that a
spring that in a spring that is a hundred times stiffer only a
hundredth part of the total work exerted by the force may be
stored. According to the invention, this principle of controlling
force and rigidity is applied to the mount of an optical element.
Embodiments of the invention are realized according to the
principle of the cardanic joint or hinge (FIG. 1-4); in the same
way embodiments comprising concentric rings are realized. In the
first case a spring having a rigidity c2 is realized by the
cardanic hinge, in the second case by the stiffness of the
intermediate ring 27 (FIG. 5), 31 (FIG. 6a) or by the stiffness of
intermediate parts 37 (FIG. 6b), 42 (FIG. 6c).
[0106] A spring having a stiffness c1 may be a thin wire, a spiral
spring or a torsion spring (bracket 47) (FIGS. 7b, c) to bend the
cardanic joint or in the alternative the intermediate ring or the
intermediate parts. In this case, both ends of the spring attack at
the middle ring a bend it in the region of attack. In a cardanic
the spring that may be a torsion spring is tensioned from the outer
ring in radial direction to the inner assembly of the optical
element.
[0107] By "optical element" mentioned heretofore, the optical
element itself or its flange is meant. According to the invention
and throughout herein, whenever a soft mount or its component is
said to be of low stiffness or less rigid, it is to be understood
that the stiffness or rigidity is being compared with that of the
position defining mounts for the optical element.
[0108] In another embodiment of the invention (FIG. 9a -c), instead
of the adjusting mechanisms 10 as shown by FIG. 4, three elastic
tunable elements 100 are provided at 120.degree.-pitch regular
intervals on the outer circumference of support member 22 and
thereby permit adjusting the optical element 23 in two degrees of
freedom by each of the elements 100.
[0109] Each of the elements 100 includes a first flat spring or
leaf spring 101 and a second flat spring or leaf spring 102. The
first flat spring 101 is bendable in the radial direction of the
lens 23 and is connected to the support member 22 and the second
elastic spring 102. The first spring 101 generates a first elastic
force from a second elastic force applied by the second elastic
spring 102 and applies the first elastic force to the support
member 22.
[0110] The spring 102 bends in the radial direction when a force is
applied on it by compression members 103 and 104 that are realized
as micrometer screws and that are borne by the outer ring 19 (cf.
FIG. 2).
[0111] Then spring 102 applies a compression force to the other
spring 101 by a small bridge 105 connecting the springs 101, 102. A
compression force is applied by members 103 and 104 if they both
are rotated in the same sense of rotation to move the optical
element 23 in radial direction.
[0112] If, however, the members 103, 104 are rotated in an opposite
sense with respect to each other, a moment force or torque is
applied to the spring 101 and is transferred to the other spring
102. Thereby, the ring 22 bearing optical element 23 is moved in
the direction tilted with respect to the optical axis (the z-axis).
Instead of compression members 103, 104 tension members may be
inserted at the same positions that exert a tension on the spring
102 to be transferred to the optical element 23 by means of the
spring 101. The members 103, 104 are inserted in insertion holes in
the ring 19 or in a lens barrel. They are disposed at equal
distances from a middle fiber 106 of spring 102.
[0113] In an alternative embodiment (FIG. 9b) the members 103, 104
are replaced by elastic rods 107, 108 that apply each a moment to
the spring 102. The rods 107, 108 are borne in an insertion hole of
ring 19. An adjusting force is applicable to the rods 107, 108 by
tuning or adjusting mechanisms 109, 110 to turn them in a direction
A. In another embodiment rods 107,108 may both be turned in the
same direction B to exert a tangential adjustment of the element
23. If, however, rods 107, 108 are tensioned in an opposite
direction B a rotational movement about a radial axis of optical
element 23 is exerted (third degree of freedom).
[0114] In another embodiment of the invention (FIG. 10) a clamping
mount 200 rigidly holds an optical element 201. Clamping mount 200
is isostatically borne by a bipod structure 202 comprising a hinge
member 203. Leaf springs 205, 206 serve to apply a static moment to
the mount 200.
[0115] However, according to the invention, the bearing member 202
permits an adjustment of the optical element 201 in at least two
degrees of freedom. Therefore, at least a single lever arm 208 is
provided that applies a moment in a direction C or in a direction D
to a bearing member 202. This permits the bearing member 202 having
solid body hinges or sufficient elasticity to be rotated about at
least two non-parallel rotational axes, thus positioning the
optical element 201 without exerting any actuating force or any
actuating moment onto the optical element 201 by means of the mount
200.
[0116] According to another embodiment an optical element 300 (FIG.
11) is positioned on a resilient mount 301. The mount 301 is
attached to an inner ring 302 that is connected to an intermediate
ring 303 by a hinge or bearing arrangement 304 or to a bearing
element holding the inner ring 302.
[0117] The intermediate ring 303 is connected to an outer ring 305
by another bearing element 306. Bearings 304 and 306 may be
cardanic elements and/or isostatic elements wherein the
intermediate ring 303 is a connecting element between the inner
ring 302 and the outer ring 305 that it permits positioning of the
optical element in at least two degrees of freedom. A gear box 307
according to the invention is applied between the inner and the
outer ring 302, 305. The gear box 307 exerts a deformation of the
intermediate ring 303, whereby the inner ring 302 is adjusted in
its position with regard to the outer ring 305.
[0118] An additional element 309 applied to the inner ring 302 is
adjustable by an actuator 310, e. g. a voice coil actuator, by an
electrostrictive element or other means that correct imaging
errors, for instance a pneumatic or hydraulic means. Thereby the
resilient mount 301 is adjusted. Hereby a deformation of the
optical element 300 may be realized to corrected any imaging errors
of element 300. This embodiment provides for arranging multiple
waveforms of the light to be exposed by the exposure apparatus.
* * * * *